Emerald Ash Borer
The emerald ash borer (Agrilus planipennis or EAB) is an invasive wood boring beetle. Despite their flashy color these beetles are difficult to spot in the wild! Adult EAB are bright, metallic green, about 1/2″ long and 1/8” wide with a flattened back. An adult EAB fits on the head of a penny.
EAB larvae are flattened and creamy white, worm-like with nested bell-shaped segments. It is the larvae that does all the harm to ash trees. The larvae tunnel under the bark and disrupt the tree’s systems that transport food and water, eventually killing it.
The emerald ash borer is an invasive beetle which threatens the native ash species in our hardwood forests and urban landscapes. EAB larvae feed on tissue in the inner bark and outer sapwood disrupting the tree’s ability to transport water and nutrients. Both healthy and stressed ash trees are vulnerable to attack and once a tree begins to show symptoms of infestation with EAB it quickly declines and dies in a few seasons. Native to Asia, EAB likely arrived in the US in the early 1990s in wood packing material but was not officially identified until 2002 in Michigan. Since its arrival in the US, EAB is responsible for the death of many millions of native ash trees. The economic impact of EAB will cost the US billions of dollars and have devastating effects on our urban and natural forest ecosystems.
EAB are strong fliers capable of flying up to several miles to infest new trees, but the most significant way EAB spreads to new areas is when we carry the beetle in infested wood material. Firewood and nursery stock, as well as, large pieces of mulch and other wood products derived from ash could potentially contain EAB larvae. EAB is just one of many significant “pests” that can spread to new area by people. Unwanted pests and plant diseases can move into new areas unknowingly in firewood or in or on live plant material. One way to help limit human assisted spread of these plant pests and pathogens is by burning firewood where you cut it. Learn more about human assisted spread of plant pests and pathogens at http://www.dontmovefirewood.org/
All eastern North American ash (Fraxinus spp.) are susceptible to attack including green, white, blue and black ash and their cultivars. The native range of these ash species covers 2⁄3 of the continental US, from Maine to Montana, south to Florida and Texas. Because they adapt to difficult growing conditions, they have been widely planted throughout the US including all the western states.
Signs and Symptoms
Usually trees are not diagnosed with emerald ash borer until severe dieback is noticed. Help slow the spread of EAB and look for signs and symptoms annually on your ash trees. Early symptoms include thinning foliage throughout the canopy. Leafy (epicormic) shoots may sprout from large branches and the main trunk. Woodpecker damage is very common and may be the first symptom of early infestation. It appears as lighter bark with ragged holes as the surface is removed by woodpeckers as they dig out larvae from galleries beneath the bark. On trees with these symptoms look for D-shaped exit holes and bark splits exposing S-shaped tunnels filled with sawdust like frass (excrement).